In an optical disk device, if the direction of the exit optical axis of the optical pickup is inclined with respect to the signal recording surface of the optical disk, an aberration may occur, and it may become impossible to correctly record and reproduce information signal. Therefore, the optical disk device is provided with a mechanism for adjusting the inclination angle (i.e., the direction of the exit optical axis) of the optical pickup with respect to the signal recording surface of the optical disk.
In the inclination angle adjustment of the optical pickup, the inclination angle adjustment in the radial direction of the optical disk, and the inclination angle adjustment in the tangential direction of the optical disk are performed. The inclination angle adjustment in the radial direction is performed by adjusting the inclination of the spindle motor (for rotating the optical disk) in the radial direction of the optical disk, or by adjusting the inclination of a main shaft for guiding the optical pickup. After the inclination angle adjustment in the radial direction is completed, the inclination angle adjustment in the tangential direction is performed by adjusting the inclination of the spindle motor in the tangential direction of the optical disk, or by adjusting the inclination of a secondary shaft (a guide shaft provided parallel to the main shaft) for guiding the optical pickup.
The above described inclination angle adjustment of the secondary shaft is performed by adjusting the heights of both ends of the secondary shaft using adjusting screws or the like. To be more specific, the following methods are known. In a first method, one end of the secondary shaft is adjusted so that the secondary shaft is parallel to the main shaft. Then, the optical disk device is brought into a reproducing state, and the heights of both ends of the secondary shaft are adjusted by the same amounts so that the secondary shaft and the main shaft are at the same heights, while monitoring the reproduced signal.
However, this first method needs two-stage adjustments including a first stage adjustment for parallelizing the secondary shaft to the main shaft, and a second stage adjustment for having the secondary shaft at the same height as the main shaft. Further, it is difficult to adjust the heights of both ends of the secondary shaft by the same amounts, and it is necessary to use an exclusive tool.
Therefore, the following second method is proposed. In the second method, the optical disk device is brought into the reproducing state. Then, the optical pickup is moved to the end portion on the disk inner circumference side, and the height of one end (an end closer to the optical pickup) of the secondary shaft is adjusted while monitoring the reproduced signal. Thereafter, the optical pickup is moved to the end portion on the outer circumference side, and the height of the other end of the secondary shaft is adjusted while monitoring the reproduced signal (see, for example, Patent Document Nos. 1 and 2).
Patent Document No. 1: Japanese Patent Publication No. 3428832 (Pages 4-5, FIG. 5).
Patent Document No. 2: Japanese Laid-Open Patent Publication No. 2002-100131 (Pages 2-3, FIG. 1).